FIG. 1 illustrates a prior art, conventional MEMS (Micro-Electro-Mechanical System) seek-scan-probe (SSP) memory device, where various components are labeled by their typical names. For simplicity, only two cantilevers are shown in FIG. 1, but in practice there is an array of cantilevers. The storage media comprises a Chalcogenide. However, other media may be used for storage, such as ferroelectric material. Electrical energy (heat) converts a Chalcogenide between its crystalline (conductive) and amorphous (resistive) phases, so that information may be stored, and read by sensing current through the storage media. The cantilever array is on a stage mover. The cantilever array may be moved laterally so that a data bit may be stored or read spatially. Each cantilever covers a specific region of the storage media to perform read, write, and erase operations over the specific region.
To perform a read, write, or erase operation, the tip of the active cantilever needs to contact the storage media so that current can flow between the tip and the media electrode underneath the storage media for resistance sensing (read operation) or electrical current passing (write and erase operations). The read, write, or erase action is performed with a pulse voltage, e.g., ground to 8 volts, applied on the media electrode with a typical duration of about 20 nano-seconds (ns). The cantilever mechanical response is insensitive to such a fast electrical pulse. The tip contact with the storage media is mainly achieved by the cantilever's bending from internal stress.
Due to process variation on the wafer, the stress-induced bending may vary significantly from cantilever to cantilever, resulting in situations in which some cantilevers are in contact with the storage media while some have inadequate bending to reach the storage media surface. In order to make sure that all cantilevers are contacting the storage media, the gap between the mover and storage media surface is usually reduced to obtain adequate contact force on the least-bent cantilevers. However, this may damage the cantilever tips.